The present invention is directed to liquid chromatography and is particularly concerned with an automatic arrangement for trapping and removing air from a liquid chromatography feed system.
In liquid chromatography a liquid sample is passed by a flowing stream of liquid solvent (the mobile phase) through a column packed with particulate matter (stationary phase). While passing through the column the various components in the sample separate from one another by adsorbing and desorbing from the stationary phase at different rates such that these individual components elute from the column at different times. The separated components then flow through a detector which responds to each component both qualitatively and quantitatively thereby providing information to the user about the separation achieved by the chromatography column.
The particulate matter in the chromatography column is generally referred to as the chromatography media and the resolution of a separation of the stream into individual components by the chromatography media is a primary measure determinant of the economic value of the chromatography.
Accordingly it is necessary to protect the chromatography media from conditions which will ruin the media including the presence of air and the presence of microbial contamination.
The presence of air in a chromatography column fills the pores of the chromatography media and blocks the liquid sample from getting to the active sites of the media. Additionally the presence of air disrupts the flow of the liquid sample as it is essential to achieve even flow of the liquid sample through the column.
Microbial or bacterial contamination is a particular problem with low pressure chromatography in that the liquid phase is aqueous and the gel media a carbohydrate. With water present bacteria can grow interfering with the ability of the media to produce a clean, pure product.
Accordingly it is highly desirable to prevent air from entering the column and to provide a bubble trap that not only excludes air from entering the column but also is of sanitary design to inhibit the growth of bacteria within the chromatography system and, in particular the chromatography column. Bubble traps are a known technique in liquid chromatography for protecting the chromatography column and more specifically the chromatography media. A typical bubble trap comprises a reservoir located at the down stream end of a system pump for delivering a liquid to a chromatography column. The reservoir supplies the liquid to the chromatography column. Any air whether from air entrapped in the liquid, or resulting from a slow leak, or from a dry line condition would be trapped in the upper portion of the reservoir above the level of the liquid therein.
Heretofore bubble traps have not been automated or have been minimally automated. The result is that during unattended operation common in liquid chromatography processes (some reaching days in duration) in the event of depletion of liquid in the bubble trap, air will eventually reach the liquid chromatography column. This problem can be minimized by increasing the bubble trap holding volume; however, this also increases the difficulty of cleaning the bubble trap, already a major concern in the biopharmceutical industry and increases system holdup volume which degrades the system effectiveness in achieving the desired separation of the mixture being processed.